1. Field of the Invention
The invention relates to an improved apparatus for producing oxygen enhanced gas from air.
2. Description of the Related Art
Oxygen inhalation therapy has been employed as a most effective method of treatment for a malady of the respiratory system such as asthma, pulmonary emphysema or chronic bronchitis. In oxygen inhalation therapy, an oxygen enhanced gas, which is produced by separating nitrogen gas from air, is supplied to the patient. For this purpose, a fractionator or an apparatus for producing an oxygen enhanced gas from air has been developed. In particular, a compact fractionator is suitable for conducting oxygen inhalation therapy domestically.
WO 93/16876 discloses a fractionator for producing an oxygen enhanced gas by separating nitrogen gas from air. The fractionator has a plurality of columns filled with an adsorbent material and rotary valve for distributing air selectively to the columns.
The fractionator produces the oxygen enhanced gas with high efficiency when the temperature of the adsorbent material is within a temperature range. However, if the temperature of the adsorbent material is out of the range due to, for example change in the air temperature, the production of the oxygen enhanced gas is much reduced.
The invention is directed to solve the prior art problems, and to provide an apparatus for producing oxygen enhanced gas from air which is improved to maintain the production efficiency at a level in spite of changes in air temperature.
The invention provides an apparatus for producing an oxygen enhanced gas for use in oxygen inhalation therapy. The apparatus includes an air source for supplying air; a plurality of columns for containing an adsorbent material for adsorbing nitrogen gas, each of the columns having first and second open ends; means for directing the air from the air source to the column through the first open ends of the respective columns; an oxygen enhanced gas tank, fluidly connected to the second open ends of the respective columns, for receiving oxygen enhanced gas from the columns; a switching mechanism, provided adjacent to the first open ends of the columns, for sequentially selectively switching columns to which the air is supplied from the air source and columns from which the adsorbed nitrogen is released for regeneration of the adsorbent material so that the respective columns repeatedly adsorb nitrogen gas and release the adsorbed nitrogen gas according to an adsorption-regeneration cycle; a temperature sensor for detecting a temperature representing the temperature of the adsorbent material; and a controller for controlling the adsorption-regeneration cycle based on the representative temperature detected by the sensor.
The temperature sensor may be preferably attached to a side wall of one of the columns.
According to a preferred embodiment, the adsorbent material may include 13X type zeolite. In this case, the controller controls the adsorption-regeneration cycle to reduce the time for adsorption of the nitrogen gas when the representative temperature is not less than 20xc2x0 C.
According to another embodiment, the adsorbent material may include 5A type zeolite. In this case, the controller controls the adsorption-regeneration cycle to reduce the time for adsorption of the nitrogen gas when the representative temperature is not more than 20xc2x0 C.
According to another feature of the invention, the apparatus may include an air source for supplying air; a plurality of columns for containing an adsorbent material for adsorbing nitrogen gas, each of the columns having first and second open ends; means for directing the air from the air source to the inside of the column through the first open ends of the respective columns; an oxygen enhanced gas tank, fluidly connected to the second open ends of the respective columns, for receiving oxygen enhanced gas from the columns; a temperature sensor for detecting a temperature representing the temperature of the adsorbent material; and a temperature controller for controlling the temperature of the adsorbent material based on the representative temperature detected by the temperature sensor.
The preferred adsorbent material for this apparatus may include 5A type zeolite, and the temperature controller heats the columns to maintain the representative temperature within a temperature range 20 to 60xc2x0 C.
The apparatus also may include a switching mechanism, provided adjacent to the first open ends of the columns, for sequentially selectively switching columns to which the air is supplied from the air source and columns from which the adsorbed nitrogen is released for regeneration of the adsorbent material so that the respective columns repeatedly adsorb nitrogen gas and release the adsorbed nitrogen gas according to an adsorption-regeneration cycle.